Methods, Apparatus, and Chemical Compositions for Selectively Coating Fiber-Based Food Containers

ABSTRACT

Methods and apparatus for vacuum forming and subsequently applying topical coatings fiber-based food containers. The slurry includes one or more of an embedded moisture barrier, vapor barrier, and oil barrier, and the topical coating comprises one or more of a vapor barrier, a moisture barrier, an oil barrier, and an oxygen barrier. For food containers having deep sidewalls, a spray coating system includes a first nozzle for applying a full cone spray pattern to the bottom surface of the container, and a second nozzle for applying a hollow cone spray pattern to the inside surfaces of the side walls.

REFERENCE TO RELATED APPLICATION

The present application is a continuation-in-part application of, andclaims priority to, U.S. patent application Ser. No. 15/220,371 filedJul. 26, 2016, the entire contents of which are hereby incorporatedherein by this reference.

TECHNICAL FIELD

The present invention relates, generally, to spray coatings for use withvacuum formed molded fiber food containers and, more particularly, toselective combinations of slurry chemistries and surface coatings toyield desired oil, water, vapor, and/or oxygen barriers.

BACKGROUND

Pollution caused by single use plastic containers and packagingmaterials is epidemic, scarring the global landscape and threateningdelicate ecosystems and the life forms that inhabit them. Single usecontainers migrate along waterways to the oceans in the form ofStyrofoam and expanded polystyrene (EPS) packaging, to-go containers,bottles, thin film bags and photo-degraded plastic pellets.

This ocean trash accumulates into massive patches of highly concentratedplastic islands located at each of our oceans' gyres. Sunlight and wavescause floating plastics to break into increasingly smaller particles,but they never completely disappear or biodegrade. Moreover, plasticparticles act as sponges for waterborne contaminants such as pesticides.Fish, turtles and even whales eat plastic objects, which can sicken orkill them. Smaller ocean animals ingest tiny plastic particles and passthem on to us when we eat seafood.

Sustainable solutions for reducing plastic pollution are gainingmomentum. However, continuing adoption requires that these solutions notonly be good for the environment, but also competitive with plasticsfrom both a performance and a cost standpoint. The present inventioninvolves replacing plastics with revolutionary technologies in moldedfiber without compromising product performance, and offers a competitivecost structure within an ecologically responsible framework.

By way of brief background, molded paper pulp (molded fiber) has beenused since the 1930s to make containers, trays and other packages, butexperienced a decline in the 1970s after the introduction of plasticfoam packaging. Paper pulp can be produced from old newsprint,corrugated boxes and other plant fibers. Today, molded pulp packaging iswidely used for electronics, household goods, automotive parts andmedical products, and as an edge/corner protector or pallet tray forshipping electronic and other fragile components. Molds are shaped as amirror image of the finished package, with a screen is attached to itssurface. A vacuum is drawn across the screen to build up fiber particlesinto the shape of the finished product.

The two most common types of molded pulp are classified as Type 1 andType 2. Type 1 is commonly used for support packaging applications with3/16 inch (4.7 mm) to ½ inch (12.7 mm) walls. Type 1 molded pulpmanufacturing, also known as “dry” manufacturing, uses a fiber slurrymade from ground newsprint, kraft paper or other fibers dissolved inwater. A mold mounted on a platen is dipped or submerged in the slurryand a vacuum is applied to the generally convex backside. The vacuumpulls the slurry onto the mold to form the shape of the package. Whilestill under the vacuum, the mold is removed from the slurry tank,allowing the water to drain from the pulp. Air is then blown through thetool to eject the molded fiber piece. The part is typically deposited ona conveyor within a drying oven.

Type 2 molded pulp manufacturing, also known as “wet” manufacturing, istypically used for packaging electronic equipment, cellular phones andhousehold items with containers that have 0.02 inch (0.5 mm) to 0.06inch (1.5 mm) walls. Type 2 molded pulp uses the same material andfollows the same basic process as Type 1 manufacturing up the pointwhere the vacuum pulls the slurry onto the mold. After this step, atransfer mold mates with the fiber package, moves the formed “wet part”to a hot press, and compresses and dries the fiber material to increasedensity and provide a smooth external surface finish. See, for example,stratasys.com/solutions/additive-manufacturing/tooling/molded-fiber;keiding.com/molded-fiber/manufacturing-process/; Grenidea TechnologiesPTE Ltd. European Patent Publication Number EP 1492926 B1 published Apr.11, 2007 and entitled “Improved Molded Fiber Manufacturing”; andafpackaging.com/thermoformed-fiber-molded-pulp/. The entire contents ofall of the foregoing are hereby incorporated by this reference.

Fiber-based packaging products are biodegradable, compostable and,unlike plastics, do not migrate into the ocean. However, presently knownfiber technologies are not well suited for use with meat and poultry,prepared food, produce, microwavable food, or as lids for beveragecontainers such as hot coffee. In particular, selectively integratingone or more oil, water, vapor, and/or oxygen barriers into the slurry,and/or selectively applying one or more of the barrier layers to all ora portion of the surface of the finished packaging product, can becumbersome, time consuming, and expensive.

Methods, apparatus, spray systems, and chemical formulations are thusneeded which overcome the limitations of the prior art.

Various features and characteristics will also become apparent from thesubsequent detailed description and the appended claims, taken inconjunction with the accompanying drawings and this background section.

BRIEF SUMMARY

Various embodiments of the present invention relate to methods, chemicalformulae, spray systems, and nozzle configurations for manufacturing andselectively applying barrier coatings to selected surfaces of vacuummolded, fiber-based packaging and container products including, interalia: i) meat, produce, horticulture, and utility containers embodyingnovel geometric features which promote structural rigidity; ii) meat,produce, and horticulture containers having embedded and/or topicalmoisture, oil, oxygen, and/or vapor barriers; iii) microwavable,oven-heated, frozen food, ready to eat, yogurt, salad, prepared foods,macaroni and cheese, and other containers embodying embedded and/ortopical moisture, oil, oxygen, and/or vapor transmission barriers,and/or retention aids to improve chemical bonding within the fibermatrix; and iv) meat containers embodying a moisture/vapor barrier whichpreserves structural rigidity over an extended shelf life.

It should be noted that the various inventions described herein, whileillustrated in the context of conventional slurry-based vacuum formprocesses, are not so limited. Those skilled in the art will appreciatethat the inventions described herein may contemplate any fiber-basedmanufacturing modality, including dry or fluff processes which may ormay not involve vacuum forming, including 3D printing techniques.

Various other embodiments, aspects, and features are described ingreater detail below.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Exemplary embodiments will hereinafter be described in conjunction withthe appended drawing figures, wherein like numerals denote likeelements, and:

FIG. 1 is a schematic block diagram of an exemplary vacuum formingprocess using a fiber-based slurry in accordance with variousembodiments;

FIG. 2 is a schematic block diagram of an exemplary closed loop slurrysystem for controlling the chemical composition of the slurry inaccordance with various embodiments;

FIG. 3 is a perspective view of the bottom side of an exemplary meattray in accordance with various embodiments;

FIG. 4 is a side elevation view of the meat tray of FIG. 3 in accordancewith various embodiments;

FIG. 5 is a top plan view of the meat tray of FIGS. 3 and 4 inaccordance with various embodiments;

FIG. 6 is an end view of the meat tray of FIG. 5 in accordance withvarious embodiments;

FIG. 7 is a schematic perspective of a spray coating system for meattrays in accordance with various embodiments; and

FIG. 8 is a schematic perspective of a spray coating system employing afull cone and hollow cone dual nozzle system for use with microwave,frozen food, prepared meals, and other food containers having deep sidewalls in accordance with various embodiments.

DETAILED DESCRIPTION OF PREFERRED Exemplary Embodiments

The following detailed description of the invention is merely exemplaryin nature and is not intended to limit the invention or the applicationand uses of the invention. Furthermore, there is no intention to bebound by any theory presented in the preceding background or thefollowing detailed description.

Various embodiments of the present invention relate to fiber-based orpulp-base products for use both within and outside of the food andbeverage industry. By way of non-limiting example, the presentdisclosure relates to particular chemical formulations of slurries andtopical films or coatings adapted to address the unique challengesfacing the food industry including oil barriers, moisture barriers,water vapor barriers, oxygen barriers, strength additives, and retentionaids, the absence of which have heretofore limited the extent to whichfiber-based products can effectively replace single use plasticcontainers in the food industry. Coupling surface coating techniques(e.g., spray coating, immersion) with novel slurry chemistries enablesfiber-based products to replace their plastic counterparts in a widevariety of applications such as, for example: frozen, refrigerated, andnon-refrigerated foods; medical, pharmaceutical, and biologicalapplications; microwavable and oven safe food containers; beverage cupsand lids; comestible and non-comestible liquids; substances whichliberate water, oil, and/or water vapor during storage, shipment, andpreparation (e.g., cooking); horticultural applications includingconsumable and landscaping/gardening plants, flowers, herbs, shrubs, andtrees; chemical storage and dispensing apparatus (e.g., paint trays);produce (including human and animal foodstuffs such as fruits andvegetables); salads; prepared foods; packaging for meat, poultry, andfish; lids; cups; bottles; guides and separators for processing anddisplaying the foregoing; edge and corner pieces for packing, storing,and shipping electronics, mirrors, fine art, and other fragilecomponents; buckets; tubes; industrial, automotive, marine, aerospaceand military components such as gaskets, spacers, seals, cushions, andthe like; and associated molds, wire mesh forms, recipes, spray systemsand spray nozzle configurations and processes, chemical formulae,tooling, slurry distribution, chemical monitoring, chemical infusion,and related systems, apparatus, methods, and techniques formanufacturing the foregoing components.

Various embodiments of spray coating techniques surround oil barriersand/or vapor barriers for microwave bowls, as well as for meat trays toaddress the phenomenon whereby water and/or oil penetrates the traysurface, and pulls off with the meat after freezing. In addition, spraycoating may have applicability to beverage lids, for example, tomitigate undesirable staining (e.g., lipstick).

In some embodiments, the microwave bowls, steamers, or trays are spraycoated on the inside surface only; other embodiments contemplate spraycoating on both the inside and outside surfaces. For spray applications,the spray nozzles may be configured to apply a spray pattern whichclosely approximates the surface being coated (e.g., circular, annular,rectangular, and the like).

Various spray, immersive, or other coating modalities employ chemistriesadapted to yield desired performance characteristics in the finishedproducts. Various chemical formulations comprise alginates (e.g., algaederivatives) mixed with a polyester emulsion and applied to a surface ofthe container to mitigate the transmission of water vapor through thecontainer wall (e.g., the bottom surface) upon heating (e.g., using amicrowave or conventional oven). Various chemical formulations may alsoinclude a calcium carbonate component to facilitate bonding of thecoating to the surface of the fiber-based container. In manyapplications, the coatings also effectively mitigate oil transmission.

These coating chemistries may be used in lieu of (or in addition to)incorporating TG8111 based fluorochemistries into the slurry, asdescribed elsewhere herein. In some embodiments, even though the surfacecoating may have secondary oil barrier attributes in addition to primaryvapor barrier and/or water barrier attributes, it may nonetheless bedesirable to also embed an oil barrier component into the slurry.

Various surface coating embodiments contemplate chemistry aspects aswell as process aspects (e.g., the manner in which the formulation isapplied to the surface(s) to achieve desired coverage objectives).Process considerations include, but are not limited to, spray dropletsize, sprayer configurations and orientations, spray geometries, as wellas “fill and go” techniques in which a container (e.g., yogurt) isfilled with a coating formulation and quickly emptied to yield a film onthe inside surface(s).

In this regard, vapor barriers (e.g., to prevent frozen foods fromdrying out while frozen) and oxygen barriers (to preserve freshness andshelf life during refrigeration) typically require complete (e.g., 100%)coverage of the protected surface, whereas moisture (e.g., water)barrier coatings (e.g., to prevent meat from sticking to the meat trayafter one or more freeze/thaw cycles or to prevent starches fromsticking to microwave bowls) can be effective at substantially less thancomplete surface coverage.

In various embodiments, spray and other coating processes may be used toapply vapor, oxygen, moisture, and/or oil barriers to surface(s) of afinished container, either in addition to or in lieu of incorporatingone or more barrier chemistries into the slurry used to vacuum mold thecontainer. In a preferred embodiment, a moisture barrier component ismixed into the slurry, and an oil and/or vapor barrier applied to theformed container, for example when only the inside surfaces are to becoated (e.g., for non-stick barriers).

Spray coating applications contemplate, inter alia, microwave bowls,frozen food, and meat trays. Depending on the application, it may bedesirable to spray coat one or more of a water, vapor, oil, and anoxygen barrier. For microwave bowls, to the extent the issue is shelflife, 100% coverage may not necessarily be required. Spray techniquesmay be used to apply water and/or vapor barriers, but also to prevent“sticking” so the meat (after one or more cycles of freezing/thawing)doesn't tear away paper fibers when removed from the tray in the frozencondition (does not require 100% coverage). Yogurt and otherapplications use spray coating for water vapor and oxygen barriers,which typically do require near 100% coverage.

Spray coating use cases generally involve: i) the chemical formulationof the coating being applied; ii) the thermophysical, rheological andviscoelastic properties; iii) the apparatus for applying the coating toone or more surfaces (or portions of a surface) of the container,package, or other workpiece; and iv) process parameters such as dryingtime and temperature.

A typical use case involving spray coating surrounds coating a meat traywith a moisture barrier to help prevent the meat from sticking to thefiber tray after freezing. A top (surface) coating may be applied (viaspray or otherwise) to reduce the extent to which the meat sticks to thetray after freezing. The coating also helps sustain the strength andrigidity of the tray even without freezing, for example while the meatand juices sit in the tray in the refrigerator.

An exemplary method of manufacturing a spray coated meat tray may beginwith an aqueous fiber based slurry comprising up to 100% OCC or anydesired combination of OCC and double-lined kraft (DLK) paper.(Alternatively, the various slurry bases described herein may comprise amixture of recycled and virgin fiber, or the slurry base may comprise100% virgin fiber (e.g., hardwood, softwood, or a combination thereof)as discussed below in conjunction with microwave bowls).

A water/moisture barrier (e.g., 2 to 5%, and preferably about 4% AKD), adry strength additive (e.g., 0.5 to 4.5% and preferably about 4% starchHercobond 6950 or modified starch), and a wet strength additive (e.g.,Kymene) may be added to the slurry. After the trays are vacuum formed(for example after being dried in the hot press for approximately 55seconds), the trays are transferred to a stacker and the stacks of traysare transferred to a spray coating station where they are de-nested anddropped into respective pockets on a conveyor whereupon a supplementalmoisture coating is applied to each tray in either a serial or parallelfashion.

In various embodiments the supplemental coating may be applied using asystem comprising two stationary nozzles disposed above the trays, witheach nozzle outputting a spray pattern in the form of a wall or curtain(much like an air knife) as the trays pass underneath. As such, eachnozzle (or combination of nozzles) produces a spray pattern terminatingin a line suitably orthogonal to the direction of workpiece travel. Inan embodiment, one nozzle may be angled forward (towards the directionof tray travel) and the other nozzle angled rearwards to ensure completecoating of the inclined sidewalls, structural ribs, and any othergeometric features.

Alternatively, for substantially flat trays with limited sidewalldepths, or for applications in which film uniformity is less important,a single curtain-type spray configuration may be employed.

One metric for evaluating whether a tray has received sufficientcoverage (e.g., has been adequately coated) involves comparing theweight of a tray before and after coating to determine whether theweight of the coating material applied to the tray satisfies apredetermined threshold value (or range). Alternatively, or in addition,the thickness of the applied film may be measured to determine whetherthe thickness of the coating satisfies a predetermined threshold value(or range of values).

In some embodiments the uniformity of the applied coating may also bemeasured and process parameters adjusted as need to facilitateuniformity of application on future trays, in this regard, uniformityinvolve at least two considerations, namely: i) whether the film layerat a local point or region is too thin such that an effective barrier isnot formed; and ii) whether the film layer at a local point or region istoo thick such that the finished tray at that point may not drythoroughly, resulting in blemishes or skinning (where a top layer of thefilm slides off or otherwise becomes detached from the film).

The coated trays are then dried in an oven in the range of 70-180° C.,and preferably about 80-110° C., and most preferably about 95° C. forapproximately one (1) minutes to remove moisture from and otherwise curethe film layer, as appropriate. An infrared (IR) sensor may be used toprobe the temperature of a meat tray at one or a plurality of points toensure that the proper curing temperature has been achieved.

For meat trays the coating composition may comprise 25% acrylic and 75%water, where the acrylic may comprise an acrylic copolymer latex orsimilar material, such as Rhobarr 110 binder available from the DOWChemical Corporation. In this context, the coating functions as ananti-stick layer to keep the top layer of the meat tray from peeling offas frozen meat is removed from the tray.

In some embodiments, some or all of the opposite side of the tray(including the bottom surface and/or exterior sidewalls) may also becoated. This reduces the extent to which frozen juices (e.g., blood,oil, water) from the meat may stick to the outside of the tray if, forexample, juice leaks around the seal between the tray and the outerplastic wrap when the package is stored on its side.

Meat trays typically do not require a separate oil barrier, although thevapor and/or anti-stick barriers may also effectively inhibit oiltransmission.

As an alternative to or in addition to an acrylic, a pea emulsion plusan alginate could also be used for meat trays, microwave bowls, and/orother packaging components.

After drying, the trays are stacked, boxed, and shipped.

The term “ready-to-eat” (RTE) trays refer to containers within whichsalads, fruits, prepared meals, and other foods are packaged using aplastic film sealed about the tray perimeter and stored, often in arefrigerator. RTE trays may be coated to provide an oxygen barrier toimprove freshness and shelf life.

RTE trays without a topical film barrier may be made by adding to anOCC/DLK slurry comprising 30-100% OCC/DLK and 0-70% virgin pulp, andpreferably about 100% OCC/DLK: i) an oil barrier comprising 1-5% andpreferably about 4% Daikin 8111; ii) a moisture/water barrier comprising2-5% and preferably about 3.5% AKD; and iii) a strengthening componentcomprising 3% starch such as Hercobond.

RTE trays with a topical film barrier may be made in substantially thesame way described above (but perhaps eliminating the 8111 oil barrierand/or increase the AKD to 4%), and also adding a topical oxygen barriercomprising an acrylic in water solution (e.g., 25% Robar 110 and 75%water). For RTE trays and containers (e.g., yogurt cups), the film istypically thicker than that described above in the context of meattrays, in order to ensure more complete (e.g., 100%) coverage.

Uncoated microwave bowls may be made using a slurry comprising up to100% virgin fiber (softwood, hardwood, or a combination thereof). In oneembodiment, the slurry base comprises about 45% bleached hardwood, about35% bleached softwood, and about 25% unbleached softwood. The slurry mayalso include an oil barrier (e.g., 2.5% 8111), a water barrier (e.g., 3%AKD), a dry strength additive (e.g., 2.5% starch), a retention additive(e.g., 0.15% Nalco), and a de-foaming component (e.g., 1.5% Expair) toremove entrained air.

Coated microwave bowls may be made using a substantially virgin fiberslurry base such as that described above in connection with uncoatedmicrowave bowls, and further including about 3% water barrier (AKD) andabout 2.5% starch, but without the oil barrier, the retention additive,and the defoamer. The coating formulation may comprise about 27.5%solids in a water solution. The 27.5% solids may comprise a suitablecombination of all or some of the following five (5) components(sometimes referred to as a DWP formulation): i) 25% acrylate; ii) 1.8%rice bran wax (which may reduce tackiness); iii) 0.4% pectin (which mayfacilitate the formation of a vapor barrier and also reduce tackiness tofacilitate de-nesting of stacked bowls); iv) 0.3% pea protein (which mayfacilitate emulsion of the rice bran wax); and v) 0.2% liquid ammoniumor other additive to adjust the pH to thereby facilitate acrylatecuring.

For bowls and other packaging components having deep sidewalls, thecurtain-type spray output terminating in a line is inadequate. Toaddress this challenge, the present inventors have developed a twonozzle spray paradigm which involves a full cone spray pattern coupledwith a hollow cone spray pattern which together provide adequatecoverage for bottom surfaces as well as sidewall features withoutoverspraying the bottom surface.

In a preferred embodiment the coating is applied to microwave bowlsusing a two nozzle system disposed above a conveyor which carries thebowls through the spray coating station. A first “full cone” nozzle isconfigured to cover the center (bottom) of each bowl, and a second“hollow cone” nozzle is configured to cover the inside sidewall of eachbowl. The full cone and hollow cone spray patterns are suitableconfigured to ensure complete coverage while minimizing excess filmthickness at the region where the full cone pattern overlaps the hollowcone pattern.

In a preferred embodiment, as the bowls or other packaging componenttravels along the conveyor, the nozzle system also travels along thesame path for a predetermined period of time, such that the nozzle ornozzles do not translate relative to a bowl during spraying.Accordingly, the nozzle(s) may remain “stationary” with respect to eachbowl without compromising throughput.

Coated yogurt cups may be made using a substantially virgin fiber slurrybase such as that described above in connection with uncoated microwavebowls, and further including about 4% water barrier (AKD) and 3% starch.In lieu of (or in addition to) the spraying methods discussed above, atopical oxygen barrier layer may be applied using either: i) a fullimmersion step in which the cup is dipped into a pool of coatingsolution to thereby coat both the inside and outside surfaces; or ii) ora “fill and dump” technique in which coating solution is poured into thecup until it is full, and thereafter dumped out to coat the insidesurfaces of the cup. In this context, the same or a more dilute (loweracrylate concentration) version of the aforementioned DWP formulationmay be employed. In addition, the poured solution may be recirculated inan open or closed loop system to reduce waste.

The coated cups may then be dried in an oven at about 95° C. for aboutone minute and thereafter, stacked, boxed, and shipped.

In traditional macaroni and cheese (mac 'n cheese) bowls the pasta isdry and the cheese is typically separately packaged in a plastic or foilenvelope; as such, an oxygen barrier layer may or may not be needed. Ifan oxygen layer is desired, it may be applied, for example, using eitherthe full immersion or pour and dump techniques (or both) describedabove. If an oxygen layer is not needed, an anti-stick coating may beapplied as described above.

An alternate version of the DWP formulation involves eliminating 0.3%pea protein (which is a powder) and using 0.05% Tween 80 (an emulsifier)to perform substantially the same function to emulsify the rice wax.

In addition, instead of using powdered pectin, we use an aqueous versionwhich is easier to mix.

Formulations for topical coatings may include the following:

Example 1 Ingredient wet basis (%) Dry basis (%) Acrylic Polymers  5-6095.78-80.43 Rice Bran Wax 0.1-12   1.92-16.09 Pea Protein Isolate0.02-2   0.38-2.68 Pectin 0.1-0.6 1.92-0.80 Aqua Ammonia 0.1-0.2 0 (pH =9.0 using 4% solution) Water 94.68-25.2  0 Total

Example 2 Ingredient wet basis (%) Dry basis (%) Acrylic Polymers 20-3095.69-88.24 Rice Bran Wax 0.6-3  2.87-8.82 Pea Protein Isolate 0.1-0.50.48-1.47 Pectin 0.2-0.5 0.96-1.47 Aqua Ammonia 0.1-0.2 0 (pH = 9.0using 4% solution) Water  79-65.8 0 Total

Example 3 Ingredient wet basis (%) Dry basis (%) Acrylic Polymers 2590.91 Rice Bran Wax 1.8 6.55 Pea Protein Isolate 0.3 1.09 Pectin 0.41.45 Aqua Ammonia 0.1 0 (pH = 9.0 using 4% solution) Water 72.4 0 Total100 100

More generally, the DWP spray coating may be described as an aqueousformulation containing in the range of 15-40% by weight total solids,and preferably in the range of 25-30%, and most preferably about 27.5%.One ingredient in this formulation may comprise acrylic polymers which,upon curing, crosslink and polymerize to facilitate forming desiredmoisture, oil, and/or oxygen barrier layers. This formulation alsocontains rice bran wax to provide non-stick properties and non-glossysurface finishing of the coated surface. The wax is emulsified with peaprotein for stable aqueous dispersal. This formulation also containspectin as a viscosity modifier for optimal adhesion to hydrophobicfibrous surface during spray coating. pH of formulation is around 9.0with added ammonia to maintain solubility of the acrylic polymers.

Exemplary methods for preparing a solution to applied as a topicalcoating will now be described in the context of a seventy-five (75)gallon batch using the following definitions:

RBW: Rice Bran Wax

PP: Pea Protein

Pec: Pectin

G: Gallons

L: Liters

kg: Kilograms

Heat 35.6 gallons of water to at least 185° F., and mix in 5.1 kg RBW athigh speed for approximately 12 minutes until the wax pellets are fullymelted and the temperature of the solution returns to 185° F. Add 0.85kg PP to the mixture over approximately one minute. Mix the PP for anadditional ten minutes or longer until no clumps are visible. Add 1.14kg Pec over 0.5 minutes and allow the contents to mix for an additional15 minutes or longer until there no clumps are visible. Continue mixingat low speed and bring the batch temperature to approximately 120° F.While mixing add 37.5 gallons Rhobarr 110 to the batch and continue tomix for ten minutes. Slowly pour 2.15 L of 4% ammonia to the batch andcontinue mixing for ten additional minutes.

Referring now to FIG. 1, an exemplary vacuum forming system and process100 using a fiber-based slurry includes a first stage 101 in which mold(not shown for clarity) in the form of a mirror image of the product tobe manufactured is envelop in a thin wire mesh form 102 to match thecontour of the mold. A supply 104 of a fiber-based slurry 104 is inputat a pressure (P1) 106 (typically ambient pressure). By maintaining alower pressure (P2) 108 inside the mold, the slurry is drawn through themesh form, trapping fiber particles in the shape of the mold, whileevacuating excess slurry 110 for recirculation back into the system.

With continued reference to FIG. 1, a second stage 103 involvesaccumulating a fiber layer 130 around the wire mesh in the shape of themold. When the layer 130 reaches a desired thickness, the mold enters athird stage 105 for either wet or dry curing. In a wet curing process,the formed part is transferred to a heated press (not shown) and thelayer 130 is compressed and dried to a desired thickness, therebyyielding a smooth external surface finish for the finished part. In adry curing process, heated air is passed directly over the layer 130 toremove moisture therefrom, resulting in a more textured finish much likea conventional egg carton.

In accordance with various embodiments the vacuum mold process isoperated as a closed loop system, in that the unused slurry isre-circulated back into the bath where the product is formed. As such,some of the chemical additives (discussed in more detail below) areabsorbed into the individual fibers, and some of the additive remains inthe water-based solution. During vacuum formation, only the fibers(which have absorbed some of the additives) are trapped into the form,while the remaining additives are re-circulated back into the tank.Consequently, only the additives captured in the formed part must bereplenished, as the remaining additives are re-circulated with theslurry in solution. As described below, the system maintains a steadystate chemistry within the vacuum tank at predetermined volumetricratios of the constituent components comprising the slurry.

Referring now to FIG. 2, is a closed loop slurry system 200 forcontrolling the chemical composition of the slurry. In the illustratedembodiment a tank 202 is filled with a fiber-based slurry 204 having aparticular desired chemistry, whereupon a vacuum mold 206 is immersedinto the slurry bath to form a molded part. After the molded part isformed to a desired thickness, the mold 206 is removed for subsequentprocessing 208 (e.g., forming, heating, drying, top coating, and thelike).

In a typical wet press process, the Hot Press Temperature Range isaround 150-250 degree C., with a Hot Press Pressure Range around 140-170kg/cm². The final product density should be around 0.5-1.5 g/cm³, andmost likely around 0.9-1.1 g/cm³. Final product thickness is about0.3-1.5 mm, and preferably about 0.5-0.8 mm.

With continued reference to FIG. 2, a fiber-based slurry comprising pulpand water is input into the tank 202 at a slurry input 210. In variousembodiments, a grinder may be used to grind the pulp fiber to createadditional bonding sites. One or more additional components or chemicaladditives may be supplied at respective inputs 212-214. The slurry maybe re-circulated using a closed loop conduit 218, adding additional pulpand/or water as needed. To maintain a steady state balance of thedesired chemical additives, a sampling module 216 is configured tomeasure or otherwise monitor the constituent components of the slurry,and dynamically or periodically adjust the respective additive levels bycontrolling respective inputs 212-214. Typically, the slurryconcentration is around 0.1-1%, most ideally around 0.3-0.5% andpreferably about 0.4-0.5%. In one embodiment, the various chemicalconstituents are maintained at a predetermined desired percent byvolume; alternatively, the chemistry may be maintained based on percentby weight or any other desired control modality.

The pulp fiber used in 202 can also be mechanically grinded to improvefiber-to-fiber bonding and improve bonding of chemicals to the fiber. Inthis way the slurry undergoes a refining process which changes thefreeness, or drainage rate, of fiber materials. Refining physicallymodifies fibers to fibrillate and make them more flexible to achievebetter bonding. Also, the refining process can increase tensile andburst strength of the final product. Freeness, in various embodiments,is related to the surface conditions and swelling of the fibers.Freeness (csf) is suitably within the range of 200-700, and preferablyabout 350-550 for many of the processes and products described herein.

Various chemical formulations (sometimes referred to herein as“chemistries”), spray coating and immersion systems, and nozzleconfigurations and product configurations for various fiber-basedpackages and containers, as well as various methods for applying topicalcoatings, will now be further described in conjunction with FIGS. 3-8.

FIG. 3 is a perspective view of a meat tray 300 illustrating theunderside 302 of the bottom surface and the outside surfaces of sidewalls 304.

FIG. 4 is a side elevation view of the meat tray 402 of FIG. 3.

FIG. 5 is a top plan view of the meat tray of FIGS. 3 and 4 illustratingthe top surface 502 of the bottom region of the tray, and respectiveside walls 504 and 506.

FIG. 6 is an end view of the meat tray 602 of FIG. 5.

FIG. 7 is a schematic perspective of a spray coating system 700 usefulfor spray coating meat trays in accordance with various embodiments.

More particularly, system 700 includes a conveyor 708 having a pocket710 for holding a tray as it is conveyed along a direction indicated byarrow 730. The tray includes a bottom panel 704 having structuralfeatures (e.g. ribs) 706 and is circumscribed by a side wall 702.

With continued reference to FIG. 7, the illustrated spray systemcomprises respective first and second spray nozzles 712 and 718. Nozzle712 is configured to discharge a substantially planar spray pattern 715bounded by side edges 714 and terminating in a line 716 substantiallyorthogonal to direction 730. Nozzle 718 is configured to discharge asubstantially planar spray pattern 721 bounded by side edges 720 andterminating in a line 716 substantially orthogonal to direction 722. Asthe tray passes underneath the spray nozzles, spray lines 716 and 722apply the coating to all or selected portions of bottom surface 704and/or the inside surfaces of sidewall 702.

FIG. 8 is a schematic perspective of a spray coating system 800including a full cone nozzle 810 configured to discharge a full conespray pattern, and a hollow cone nozzle 814 configured to discharge anannular (or “doughnut”) shaped spray pattern. In particular, system 800is configured to apply a full cone spray pattern 812 to an inside bottomsurface 802 of the workpiece (bowl). System 800 is further configured toapply a hollow cone spray pattern 816 to the inside surface of theworkpiece side walls 804.

With continued reference to FIG. 8, conveyor 806 is configured to carrytrays along a direction defined by arrow 830 (to the right in FIG. 8).In one embodiment, conveyor 806 may be configured to sequentially indexin the direction of arrow 830 to thereby position successive trays understationary nozzles 810, 814 suspended from stationary platen 820. Inthis position, the bowl on the left may have its bottom spray coatedwhile the bowl on the right has its sidewalls spray coated. Afterindexing to the next position, the bowl previously underneath nozzle 810is then disposed under nozzle 814, and so on.

In an alternate embodiment, total workpiece throughput may be increasedby operating conveyor 806 in a continuous fashion (as opposed tosequentially indexing). In order to maintain positional registrationbetween the nozzle system and the underlying workpieces duringapplication of the spray coating, platen 820 may be configured to travelto the right along with conveyor 830 to temporarily suspend relativemotion between the nozzles, and thereafter shift leftwardly to align thenozzles with the next series of workpieces to be coated.

While FIG. 8 illustrates two workpieces and one of each of a full coneand hollow cone nozzle, those skilled in the art will appreciate thatthe system may be scaled to accommodate any number of nozzles andworkpieces for each reciprocating operation of platen 820.

As briefly mentioned above, the various slurries used to vacuum moldcontainers according to the present invention comprises a fiber basemixture of pulp and water, with added chemical components to impartdesired performance characteristics tuned to each particular productapplication. The base fiber may include any one or combination of atleast the following materials: softwood (SW), bagasse, bamboo, oldcorrugated containers (OCC), and newsprint (NP). Alternatively, the basefiber may be selected in accordance with the following resources, theentire contents of which are hereby incorporated by this reference:“Lignocellulosic Fibers and Wood Handbook: Renewable Materials forToday's Environment,” edited by Mohamed Naceur Belgacem and AntonioPizzi (Copyright 2016 by Scrivener Publishing, LLC) and available athttps://books.google.com/books?id=jTL8CwAAQBAJ&printsec=frontcover#v=onepage&q&f=false; “Efficient Use of Flourescent Whitening Agents and Shading Colorantsin the Production of White Paper and Board” by Liisa Ohlsson and RobertFedere, Published Oct. 8, 2002 in the African Pulp and Paper Week andavailable attappsa.co.za/archive/APPW2002/Title/Efficient_use_of_fluorescent_w/efficient_use_of_fluorescent_w.html; Cellulosic Pulps, Fibres and Materials: Cellucon '98Proceedings, edited by J F Kennedy, G O Phillips, P A Williams,copyright 200 by Woodhead Publishing Ltd. and available atbooks.google.com/books?id=xO2iAgAAQBAJ&printsec=frontcover#v=onepage&q&f=false;and U.S. Pat. No. 5,169,497 A entitled “application of Enzymes andFlocculants for Enhancing the Freeness of Paper Making Pulp” issued Dec.8, 1992.

For vacuum molded produce containers manufactured using either a wet ordry press, a fiber base of OCC or OCC/DLK and NP may be used, where theOCC/DLK component is between 50%-100%, and preferably about 70% OCC/DLKand 30% NP or VNP, with an added moisture/water repellant in the rangeof 1%-10% by weight, and preferably about 1.5%-4%, and most preferablyabout 4%. In a preferred embodiment, the moisture/water barrier maycomprise alkyl ketene dimer (AKD) (for example, Hercon 79, Hercon 80)and/or long chain diketenes, available from FOBCHEM atfobchem.com/html_products/Alkyl-Ketene-Dimer%EF%BC%88AKD-WAX%:EF%BC%89.html#,V0zozvkrKUk;and Yanzhou Tiancheng Chemical Co., Ltd. atyztianchengchem.com/en/index.php?m=content&c=index&a=show&catid=38&id=124&gclid=CPbn65aUg80CFRCOaQod0JUGRg.

In order to yield specific colors for molded pulp products, cationic dyeor fiber reactive dye may be added to the pulp. Fiber reactive dyes,such as Procion MX, bond with the fiber at a molecular level, becomingchemically part of the fabric. Also, adding salt, soda ash and/orincrease pulp temperature will help the absorbed dye to be furtherlylocked in the fabric to prevent color bleeding and enhance the colordepth.

To enhance structural rigidity, a starch component may be added to theslurry, for example, liquid starches available commercially as Topcat®L98 cationic additive (or Hercobond 6950 available from Solenis LLC),Hercobond, and Topcat® L95 cationic additive (available from PenfordProducts Co. of Cedar Rapids, Iowa). Alternatively, the liquid starchcan also be combined with low charge liquid cationic starches such asthose available as Penbond® cationic additive and PAF 9137 BR cationicadditive (also available from Penford Products Co., Cedar Rapids, Iowa).

For dry press processes, Topcat L95 or Hercobond 6950 may be added as apercent by weight in the range of 0.5%-10%, and preferably about 1%-7%,and particularly for products which need maintain strength in a highmoisture environment most preferably about 6.5%; otherwise, mostpreferably about 1.5-2.0%. For wet press processes, dry strengthadditives such as Topcat L95 or Hercobond 6950 which are made frommodified polyamines that form both hydrogen and ionic bonds with fibersand fines. Dry strength additives help to increase dry strength, as wellas drainage and retention, and are also effective in fixing anions,hydrophobes and sizing agents into fiber products. Those additives maybe added as a percent by weight in the range of 0.5%-10%, and preferablyabout 1%-6%, and most preferably about 3.5%. In addition, both wet anddry processes may benefit from the addition of wet strength additives,for example solutions formulated with polyamide-epichlorohydrin (PAE)resin such as Kymene 920A or 1500 or similar component available fromAshland Specialty Chemical Products at ashland.com/products. In apreferred embodiment, Kymene 920A or 1500 may be added in a percent byvolume range of 0.5%-10%, and preferably about 1%-4%, and mostpreferably about 2% or equal amount with dosing of dry strengthadditives. Kymene 920A or 1500 is of the class of polycationic materialscontaining an average of two or more amino and/or quaternary ammoniumsalt groups per molecule. Such amino groups tend to protonate in acidicsolutions to produce cationic species. Other examples of polycationicmaterials include polymers derived from the modification withepichlorohydrin of amino containing polyamides such as those preparedfrom the condensation adipic acid and dimethylene triamine, availablecommercially as Hercosett 57 from Hercules and Catalyst 3774 fromCiba-Geigy.

The present inventor has determined that molded fiber containers can berendered suitable as single use food containers suitable for use inmicrowave, convection, and conventional ovens by embedding barrierchemistries into the slurry, adding a topical coating to the finishedvacuum formed container, or both. In particular, the slurry and/ortopical coating chemistry should advantageously accommodate one or moreof the following three performance metrics: i) moisture barrier; ii) oilbarrier; and iii) water vapor (condensation) barrier to avoid condensatedue to placing the hot container on a surface having a lower temperaturethan the container.

In this context, the extent to which water vapor permeates the containeris related to the porosity of the container, which the present inventionseeks to reduce. That is, even if the container is effectivelyimpermeable to oil and water, it may nonetheless compromise the userexperience if water vapor permeates the container, particularly if thewater vapor condenses on a cold surface, leaving behind a moisture ring.The present inventor has further determined that the condensate problemis uniquely pronounced in fiber-based applications because water vaportypically does not permeate a plastic barrier.

Accordingly, for microwavable containers the present inventioncontemplates a fiber or pulp-based slurry including a water barrier, oilbarrier, and water vapor barrier, and an optional retention aid. In anembodiment, a fiber base of softwood (SW)/bagasse at a ratio in therange of about 10%-90%, and preferably about 7:3 may be used. As amoisture barrier, AKD may be used in the range of about 0.5%-10%, andpreferably about 1.5%-4%, and most preferably about 3.5%. As an oilbarrier, the grease and oil repellent additives are usually water basedemulsions of fluorine containing compositions of fluorocarbon resin orother fluorine-containing polymers such as UNIDYNE TG 8111 or UNIDYNETG-8731 available from Daikin or World of Chemicals atworldofchemicals.com/chemicals/chemical-properties/unidyne-tg-8111.html.The oil barrier component of the slurry (or topical coat) may comprise,as a percentage by weight, in the range of 0.5%-10%, and preferablyabout 1%-4%, and most preferably about 2.5%. As a retention aid, anorganic compound such as Nalco 7527 available from the Nalco Company ofNaperville, Ill. May be employed in the range of 0.1%-1% by volume, andpreferably about 0.3%. Finally, to strengthen the finished product, adry strength additive such as an inorganic salt (e.g., Hercobond 6950available atsolenis.com/en/industries/tissue-towel/innovations/hercobond-dry-strength-additives/;see also sfm.state.or.us/CR2K_SubDB/MSDS/HERCOBOND_6950.PDF) may beemployed in the range of 0.5%-10% by weight, and preferably about1.5%-5%, and most preferably about 4%.

As mentioned, vapor barrier performance is directly impacted by porosityof the fiber tray. Reducing the porosity of the fiber tray and, hence,improving vapor barrier performance can be achieved using at least twoapproaches. One is by improving freeness of the tray material bygrinding the fibers. The second way is by topical spray coating using,for example, Daikin 52066, which is a water based long chainFluorine-containing polymer. Spray coating may be implemented using inthe range of about 0.1%-3% by weight, and preferably about 0.2%-1.5%,and most preferably about 1%.

Presently known meat trays, such as those used for the display ofpoultry, beef, pork, and seafood in grocery stores, are typically madeof plastic based materials such as polystyrene and Styrofoam, primarilybecause of their superior moisture barrier properties. The presentinventor has determined that variations of the foregoing chemistriesused for microwavable containers may be adapted for use in meat trays,particularly with respect to the moisture barrier (oil and porositybarriers are typically not as important in a meat tray as they are in amicrowave container).

Accordingly, for meat containers the present invention contemplates afiber or pulp-based slurry including a water barrier and an optional oilbarrier. In an embodiment, a fiber base of softwood (SW)/bagasse and/orbamboo/bagasse at a ratio in the range of about 10%-90%, and preferablyabout 7:3 may be used. As a moisture/water barrier, AKD may be used inthe range of about 0.5%-10%, and preferably about 1%-4%, and mostpreferably about 4%. As an oil barrier, a water based emulsion may beemployed such as UNIDYNE TG 8111 or UNIDYNE TG-8731. The oil barriercomponent of the slurry (or topical coat) may comprise, as a percentageby weight, in the range of 0.5%-10%, and preferably about 1%-4%, andmost preferably about 1.5%. Finally, to strengthen the finished product,a dry strength additive such as Hercobond 6950 may be employed in therange of 0.5%-10% by weight, and preferably about 1.5%-4%, and mostpreferably about 4%.

As discussed above in connection with the produce containers, the slurrychemistry and/or spray coating chemistry may be combined with structuralfeatures to provide prolonged rigidity over time by preventingmoisture/water from penetrating into the tray.

A method of manufacturing a meat tray is thus provided. The methodincludes: providing a wire mesh mold approximating the shape of the meattray; preparing an aqueous fiber based slurry comprising at least one ofold corrugated containers (OCC) and double-lined kraft (DLK) paper;adding an embedded moisture barrier to the slurry; immersing the mold inthe slurry; drawing a vacuum across the mold within the slurry until adesired thickness of fiber particles accumulates at a surface of themold; removing the accumulated particles from the mold; drying andpressing the accumulated particles in a press to thereby form the meattray; transferring the meat tray from the press to a coating station;and applying a supplemental moisture barrier layer to a surface of themeat tray at the coating station.

In an embodiment, the embedded moisture barrier comprises 2%-5% alkylketene dimer (AKD).

In an embodiment, the method further includes adding a dry strengthadditive to the slurry.

In an embodiment, the dry strength additive comprises 0.5%-4.5% starch.

In an embodiment, the coating station comprises: a spray system; and aconveyor configured to move the meat tray along a direction of travelinto engagement with the spray system.

In an embodiment, the spray system comprises a first nozzle configuredto discharge a first predetermined spray pattern onto the meat tray.

In an embodiment, the first predetermined spray pattern comprises asubstantially vertical curtain terminating in a line at the meat tray,the line having a predetermined thickness and oriented substantiallyorthogonal to the direction of travel.

In an embodiment, the spray system further includes a second nozzleconfigured to discharge a second predetermined spray pattern onto themeat tray, wherein the first spray pattern is angled toward thedirection of travel and the second spray pattern is angled away from thedirection of travel.

In an embodiment, the supplemental moisture barrier layer comprises anacrylic copolymer latex in an aqueous solution.

In an embodiment, the supplemental moisture barrier layer comprises anapproximately 1:3 solution of acrylic and water.

A method is also provided for manufacturing a microwave bowl of the typecharacterized by a substantially flat, circular, bottom region boundedby a circumferential sidewall. The method includes: providing a wiremesh mold approximating the shape of the bowl; preparing an aqueousfiber based slurry comprising at least one of hardwood virgin fiber andsoftwood virgin fiber; adding an embedded moisture barrier to theslurry; immersing the mold in the slurry; drawing a vacuum across themold within the slurry until a desired thickness of fiber particlesaccumulates at a surface of the mold; removing the accumulated particlesfrom the mold; drying and pressing the accumulated particles in a pressto thereby form the bowl; transferring the bowl from the press to acoating station; and applying a topical oil barrier layer to at least aportion of the bowl at the coating station.

In an embodiment, the embedded moisture barrier comprises 2%-5% alkylketene dimer (AKD).

In an embodiment, the method further includes adding a dry strengthadditive to the slurry, wherein the dry strength additive comprises0.5%-4.5% starch.

In an embodiment, the topical oil barrier layer comprises about 27.5%solids in a water solution.

In an embodiment, the solids comprise acrylate, rice bran wax, pectin,and pea protein.

In an embodiment, the coating station includes: a spray system; and aconveyor configured to move the bowl along a direction of travelunderneath the spray system.

In an embodiment, the spray system includes: a first nozzle configuredto discharge a full cone spray pattern onto the bottom region of thebowl; and a second nozzle configured to discharge a hollow cone spraypattern onto the inside surface of the circumferential sidewall.

In an embodiment, the method further includes the step of moving thespray system along the direction of travel such that: i) the firstnozzle is disposed above and remains stationary with respect to the bowlfor a first predetermined period of time; and ii) the second nozzle isdisposed above and remains stationary with respect to the bowl for asecond predetermined period of time.

In an embodiment, the first period of time is one of: i) greater than;ii) equal to; and iii) less than the second period of time.

A method is provided for manufacturing a fiber based microwave bowl ofthe type including a substantially circular bottom portion bounded by aninclined circumferential side wall. The method may include the steps of:providing a wire mesh mold approximating the shape of the bowl;preparing an aqueous fiber based slurry comprising up to 100% virginfiber; adding an embedded moisture barrier to the slurry; immersing themold in the slurry; drawing a vacuum across the mold within the slurryuntil a desired thickness of fiber particles accumulates at a surface ofthe mold; removing the accumulated particles from the mold; drying andpressing the accumulated particles in a press to thereby form the bowl;transferring the bowl from the press to a coating station; and applyingan acrylic based oil barrier layer to a surface of the bowl at thecoating station.

In an embodiment, the embedded moisture barrier comprises 2%-5% alkylketene dimer (AKD).

In an embodiment, the oil barrier layer comprises a calcium carbonatecomponent to facilitate bonding to a bowl surface.

In an embodiment, the oil barrier layer comprises a pea emulsion.

In an embodiment, the oil barrier layer comprises an alginate.

In an embodiment, the oil barrier layer comprises an aqueous solutionincluding about 25% acrylate and a first supplemental componentconfigured to reduce tackiness.

In an embodiment, the first supplemental component comprises about 1.8%rice bran wax.

In an embodiment, the first supplemental component comprises about 0.4%pectin.

In an embodiment, the oil barrier layer comprises a second supplementalcomponent configured to facilitate emulsion of the first supplementalcomponent.

In an embodiment, the second supplemental component comprises about 0.3%pea protein.

In an embodiment, the oil barrier layer comprises a third supplementalcomponent configured to adjust the PH level of the oil barrier coatingto thereby facilitate acrylate curing.

In an embodiment, the third supplemental component comprises about 0.2%liquid ammonium.

In an embodiment, the coating station comprises: a spray system; and aconveyor configured to move the bowl along a direction of travel intoengagement with the spray system.

In an embodiment, the spray system comprises a first nozzle configuredto discharge a full cone spray pattern onto the bottom of the bowl.

In an embodiment, the spray system comprises a second nozzle configuredto discharge a hollow cone spray pattern onto an inside surface of thesidewall.

In an embodiment, the oil barrier layer comprises an approximately 1:3solution of acrylic and water.

A method is also provided for manufacturing a microwave bowl of the typecharacterized by a substantially flat, circular, bottom region boundedby a circumferential sidewall, comprising the steps of: providing a wiremesh mold approximating the shape of the bowl; preparing an aqueousfiber based slurry comprising at least one of hardwood virgin fiber andsoftwood virgin fiber; adding an embedded moisture barrier to theslurry; immersing the mold in the slurry; drawing a vacuum across themold within the slurry until a desired thickness of fiber particlesaccumulates at a surface of the mold; removing the accumulated particlesfrom the mold; drying and pressing the accumulated particles in a pressto thereby form the bowl; transferring the bowl from the press to acoating station; and applying a topical oil barrier layer to at least aportion of the bowl at the coating station, the topical oil barrierlayer comprising about 27.5% solids in a water solution.

In an embodiment, the solids comprise acrylate, rice bran wax, pectin,and pea protein.

A microwave bowl may be manufactured using any of the methods describedherein.

While the present invention has been described in the context of theforegoing embodiments, it will be appreciated that the invention is notso limited. For example, the various spray systems and nozzleconfigurations, slurry chemistries, and spray coat chemistries may beadjusted to accommodate additional applications based on the teachingsof the present invention.

As used herein, the word “exemplary” means “serving as an example,instance, or illustration.” Any implementation described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other implementations, nor is it intended to beconstrued as a model that must be literally duplicated.

While the foregoing detailed description will provide those skilled inthe art with a convenient road map for implementing various embodimentsof the invention, it should be appreciated that the particularembodiments described above are only examples, and are not intended tolimit the scope, applicability, or configuration of the invention in anyway. To the contrary, various changes may be made in the function andarrangement of elements described without departing from the scope ofthe invention.

1. A method of manufacturing a meat tray, comprising the steps of:providing a wire mesh mold approximating the shape of the meat tray;preparing an aqueous fiber based slurry comprising at least one of oldcorrugated containers (OCC) and double-lined kraft (DLK) paper; addingan embedded moisture barrier to the slurry; immersing the mold in theslurry; drawing a vacuum across the mold within the slurry until adesired thickness of fiber particles accumulates at a surface of themold; removing the accumulated particles from the mold; drying andpressing the accumulated particles in a press to thereby form the meattray; transferring the meat tray from the press to a coating station;and applying a supplemental moisture barrier layer to a surface of themeat tray at the coating station.
 2. The method of claim 1, wherein theembedded moisture barrier comprises 2%-5% alkyl ketene dimer (AKD). 3.The method of claim 1, further comprising: adding a dry strengthadditive to the slurry.
 4. The method of claim 3, wherein the drystrength additive comprises 0.5%-4.5% starch.
 5. The method of claim 1,wherein the coating station comprises: a spray system; and a conveyorconfigured to move the meat tray along a direction of travel intoengagement with the spray system.
 6. The method of claim 5, wherein thespray system comprises a first nozzle configured to discharge a firstpredetermined spray pattern onto the meat tray.
 7. The method of claim6, wherein the first predetermined spray pattern comprises asubstantially vertical curtain terminating in a line at the meat tray,the line having a predetermined thickness and oriented substantiallyorthogonal to the direction of travel.
 8. The method of claim 6, whereinthe spray system further comprises a second nozzle configured todischarge a second predetermined spray pattern onto the meat tray,wherein the first spray pattern is angled toward the direction of traveland the second spray pattern is angled away from the direction oftravel.
 9. The method of claim 1, wherein the supplemental moisturebarrier layer comprises an acrylic copolymer latex in an aqueoussolution.
 10. The method of claim 1, wherein the supplemental moisturebarrier layer comprises an approximately 1:3 solution of particulatesand water.
 11. A method of manufacturing a microwave bowl of the typecharacterized by a substantially flat, circular, bottom region boundedby a circumferential sidewall, comprising the steps of: providing a wiremesh mold approximating the shape of the bowl; preparing an aqueousfiber based slurry comprising at least one of hardwood virgin fiber andsoftwood virgin fiber; adding an embedded moisture barrier to theslurry; immersing the mold in the slurry; drawing a vacuum across themold within the slurry until a desired thickness of fiber particlesaccumulates at a surface of the mold; removing the accumulated particlesfrom the mold; drying and pressing the accumulated particles in a pressto thereby form the bowl; transferring the bowl from the press to acoating station; and applying a topical oil barrier layer to at least aportion of the bowl at the coating station.
 12. The method of claim 11,wherein the embedded moisture barrier comprises 2%-5% alkyl ketene dimer(AKD).
 13. The method of claim 11, further comprising: adding a drystrength additive to the slurry, wherein the dry strength additivecomprises 0.5%-4.5% starch.
 14. The method of claim 11, wherein thetopical oil barrier layer comprises about 27.5% solids in a watersolution.
 15. The method of claim 14, wherein the solids comprise atackiness component and an emulsifier.
 16. The method of claim 11,wherein the coating station comprises: a spray system; and a conveyorconfigured to move the bowl along a direction of travel underneath thespray system.
 17. The method of claim 16, wherein the spray systemcomprises: a first nozzle configured to discharge a full cone spraypattern onto the bottom region of the bowl; and a second nozzleconfigured to discharge a hollow cone spray pattern onto the insidesurface of the circumferential sidewall.
 18. The method of claim 16,further comprising the step of: moving the spray system along thedirection of travel such that: i) the first nozzle is disposed above andremains stationary with respect to the bowl for a first predeterminedperiod of time; and ii) the second nozzle is disposed above and remainsstationary with respect to the bowl for a second predetermined period oftime.
 19. The method of claim 18, wherein the first period of time isone of: i) greater than; ii) equal to; and iii) less than the secondperiod of time.
 20. A microwave bowl made from the method of claim 17.